Acids and Bases
Acids and Bases
Understand and differentiate between strong acids, strong bases, weak acids and weak bases.
- Conjugate base: an acid that lost its hydrogen ion
- Conjugate acid: a base that gained a hydrogen ion
- Strong acid: dissociates 100% into ions
- Weak acid: does not dissociate 100%
- Strong base: 100% ionized in solution
- Weak base: less than 100% ionized
Strong Acid | Weak Acid |
|---|---|
Hydrobromic acid (HBr) | Formic acid (HCOOH) |
Perchloric acid (HClO4) | Acetic acid (CH3COOH) |
Hydrochloric acid (HCl) | Trichloroacetic (CCl3COOH) |
Hydroiodic acid (HI) | Hydrofluoric (HF) |
Chloric acid (HClO3) | Hydrocyanic (HCN) |
Sulfuric acid (H2SO4) | Hydrogen sulfide (H2S) |
Nitric acid (HNO3) | Water (H2O) |
Strong Base | Weak Base |
|---|---|
Sodium hydroxide (NaOH) | Ammonia (NH3) |
Potassium hydroxide (KOH) | Trimethyl ammonia (N(CH3)3) |
Lithium hydroxide (LiOH) | Pyridine (C5H5N) |
Rubidium hydroxide (RbOH) | Ammonium hydroxide (NH4OH) |
Cesium hydroxide (CsOH) | Water (H2O) |
Calcium hydroxide (Ca(OH)2) | HS- |
Barium hydroxide (Ba(OH)2) | Conjugate bases |
Strontium hydroxide (Sr(OH)2) |
Understand PH expression and the significance of pH.
- pH is a unit that describes the acidity and alkalinity of a solution.
- pH is important for oxygen transport, enzyme activity and generation of metabolic energy.
- Many biological reactions are dependent on the charge of the molecule, which is determined by their ability to accept or release a proton.
- Which depends on the pH of the solution.
- In most biological solutions H+ conc is very low.
- pH= -log [H+]
- pH can be measured via indicator dyes (litmus)
- Accurate pH determination done via glass electrode.
- pH can be used in diagnosis of diseases
- Diabetes results in lower pH (acidosis)
- Diseases that affect secretion of bicarbonate through the kidneys result in higher pH (alkalosis).
- Urine pH can be affected by acid base status.
- Higher pH indicates UTI from urease producing bacteria.
Explain buffer systems, their behavior and significance.
- Buffer solution- one that resists pH change on addition of small quantity of acid/base
- Acidic buffer- weak acid and its salt with its conjugate base
- CH3COOH/CH3COONa
- Basic buffer- weak base with its salt (main contributor of ions) with its conjugate acid
- NH4OH/NH4Cl
- Body fluids protected against changes in pH by buffering systems
- Excess acids and bases are eliminated via kidney and lungs.
- Acids produced by the body are carbonic acid, sulfuric acid, phosphoric acid, lactic acid, citric acid, ammonium ions and ketone bodies.
- Intracellular buffer systems
- Phosphate
- Protein
- Hemoglobin
- Amino acid
- Extracellular buffer systems
- Protein
- Carbonic acid-bicarbonate
- Plasma protein
- Amino acids
- Chemical buffer system-first line of defense
- Bicarbonate
- Phosphate
- Protein
- Physiological buffers- second line of defense
- Respiratory mechanism (CO2 excretion)
- Renal mechanism (H+ excretion)
Understand the Henderson-Hasselbalch equation and its applications.
- Used to calculate pH of a buffer solution
- Assumed that A- and HA are equal to their initial concentrations
- pH= pKa + log (
- pKa= -log of acid dissociation constant
- [A-]= conc of concentration base
- [HA]= conc of acid
Applications
- pKa shows how strong (lower #) or weak (higher #) an acid is; predict what a molecule will do at a specific pH.
- Solubility can be determined from pH.
- Can determine the protein isoelectric point (where proteins don’t donate or accept protons)